Case Studies

Today, vehicle manufacturers vitally need more efficiency in HVAC systems to successfully increase normal vehicle fuel economy, meet future CAFE standards and increase the driving range in hybrid and electric vehicles.  The recent introduction of water-cooled battery technology has complicated hybrid vehicle HVAC and refrigerant systems. In high ambient temperatures, the battery temperature must be precisely controlled to prevent damage or limit vehicle range capability. OEMs have also discovered that total refrigerant flow shut-off is needed in multiple evaporator and chiller systems when one of the cooling components is off or not needed.

The Innovative Solution

To meet vehicle manufacturer needs, SANHUA Automotive has developed an electronically controlled electronic expansion valve (EXV), which allows quicker response to changes in operating conditions and flexibility in superheat regulation.  This EXV enables a number of system control strategies, which ultimately lead to improved overall system efficiency through superheat optimization for increased COP or better A/C system performance.

The automotive EXV was designed to meet rigid automotive OEM specifications, such as lower mass, more internal LIN diagnostics, greater durability, higher temperature exposure and better noise and vibration performance characteristics.

The new EXV, which can be controlled via a LIN or PWM signal, is available for R134a, R1234yf, R410a and R744 refrigerant systems.  Since there is no sensing gas or diaphragm, the EXV can be optimized to perform well with all refrigerants.  The SANHUA Automotive EXV is capable of controlling flow from zero “totally shut-off” to maximum flow in 1-, 2- or 3-ton valve sizes. The EXV can also be combined with a hybrid vehicle battery chiller to more finely control the battery temperature and balance the refrigerant system COP between the chiller and passenger evaporators.

In a SANHUA Automotive EXV, the valve opening is controlled by smart action stepper motor technology. Based on vehicle and ambient conditions, the OEM controller calculates the desired evaporator superheat and valve position. Valve position is communicated to the internal EXV microprocessor via a LIN or PWM bus. The EXV microprocessor will generate an internal signal required to bring the valve to the desired position.

SAE J12275 Mobile A/C testing has proven that a SANHUA Automotive EXV can improve the refrigerant system COP of a typical passenger vehicle by more than 10 percent when tested at various points along the test matrix.  Studies have also indicated that an EXV can be especially effective in maximizing internal heat exchanger system performance.  This EXV can precisely control compressor inlet superheat to achieve higher system efficiency by optimizing evaporator and IHX heat transfer more effectively than a conventional TXV.  This superior, responsive, and stable superheat control reduces A/C compressor loads, which results in improved fuel economy, compressor reliability and refrigerant system NVH quality.

Additional investigations have shown that the SANHUA EXV control can increase a “start-stop” engine system “off time” by maintaining evaporator flow control even when the vehicle engine and compressor are not running, thereby maintaining passenger A/C comfort in traffic stop conditions by as much as 20 percent and enabling more engine-off fuel economy benefits.

The SANHUA EXV provides the ability to use just one HVAC module assembly or one compressor part number for multiple vehicle models because the set point is a LIN or PWM software control variable.  It is also capable of remote underhood mounting away from the HVAC module to improve packaging space.